Determination of heavy metal concentrations in plants exposed to different degrees of pollution using ICP-AES

Plant samples (Plantago lanceolata - narrow leaf plantain and Cichorium endiviae - endive) were collected in the surroundings of heavy metal emission sources and in other less contaminated areas. After digestion in a closed microwave system using HNO(3), the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn were determined using ICP-AES. Detection limits for all the elements of interest are given. Differences in heavy metal uptake rate between both plant species were observed. The uptake is more intensive for endive than for narrow leaf plantain. High concentrations of some heavy metals were determined in the unwashed plant samples as a result of exposure to aerosols. Tukey's statistical test was used to confirm the discrepancy of Cr concentration in plant samples from various areas. Washing the leaves with water was found to remove a large amount of water-soluble aerosols.     

Insight into the extractability of metals from soils using an implementation of the linear adsorption isotherm model

This paper deals with an often overlooked artifact in sequential and single extraction of metals from soils, viz. the volume to mass (V/m) ratio as a potential source for inadequate extraction yields. We offer a theoretical framework to get a grip on this intricate parameter and came up with a model based on a linear adsorption isotherm to derive the correct maximal metal extractability for a certain extractant. We verified the model experimentally using 0.1 mol l⁻¹ nitric acid for extraction of seven metals (Cr, Co, Cu, Cd, Pb, Ni and Zn) from an urban soil sample, and concluded that commonly used V/m ratios in the range of 10-40 ml g⁻¹ may give as much as 50% too low extraction yields. Thus, a strong caveat is in place as to be very critical what V/m ratios to use and preferably apply the model derived to obtain the correct maximal extractability using a variable V/m ratio method.     

Processes associated with ionic current rectification at a 2D-titanate nanosheet deposit on a microhole poly(ethylene terephthalate) substrate

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolyte-filled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10-μm thickness on a 6-μm-thick poly(ethylene-terephthalate) (PET) substrate with a 20-μm diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of − 37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca²⁺ and Mg²⁺ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu₄⁺ is shown to ‘invert’ the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed.

     

Simultaneous quantification of curcuminoids and xanthorrhizol in Curcuma xanthorrhiza by high-performance liquid chromatography

A new method for simultaneous quantification of curcuminoids and xanthorrhizol (XNT) in Curcuma xanthorrhiza was developed and validated using high-performance liquid chromatography with diode-array UV–Vis detector. The chromatographic separation was achieved on a Phenomenex C18 at room temperature with the mobile-phase acetonitrile ?0.001% formic acid in gradient elution system and delivered at a flow rate of 1?mL/min. Detection wavelength 425?nm was used for curcuminoids and 224?nm for XNT. System suitability, linearity, precision, accuracy, limit of detection, limit of quantitation, and stability were evaluated and were found in good agreement with Association of Official Analytical Chemists guidelines for single-laboratory validation. The proposed method was found to be precise, accurate, and reliable and also could be applied for the simultaneous quantitative analysis of curcuminoids and XNT in C. xanthorriza raw material and its herbal medicinal product.     

Effective electrodeposition of Co-Ni-Cu alloys nanoparticles in the presence of alkyl polyglucoside surfactant

The effect of alkyl polyglucoside (APG) surfactant on the electrodeposition Co-Ni-Cu alloys nanoparticles has been investigated. In a typical electrodeposition experiment, it was found that as prepared Co-Ni-Cu alloys nanoparticles characteristics, such as size homogeneity, density, dispersion on the electrode substrate and the chemicals composition, depended strongly on the concentration of APG used in the reaction as well as the applied deposition potential. For the case of chemicals composition, low APG concentration (below CMC) was found to be effective for the preparation of excellent composition of the nanoalloys. Meanwhile, for the case of size homogeneity, density, and dispersion on the surface, high APG concentration (above CMC) and high deposition potential were preferred. It was also found that, at concentration above the CMC, the APG surfactant showed a metals ions deposition inhibition characteristic that caused increasing in the electrodeposition overpotential of the entire metals ions, namely cobalt, nickel and copper. As the result the copper was found to place a high percentage in the nanoalloys deposits. Owing to its simple procedure in controlling the composition and the nanoalloys growth characteristic, present approach should find a potential application in preparing Co-Ni-Cu magnetic nanoparticles for used in currently existing applications.     

Photonic true-time delay unit for broadband adaptive nulling in antenna arrays

An Opto-VLSI-based (VLSI: very-large-scale-integration) tunable true-time delay (TTD) generation unit used for adaptive null steering in phased array antennas is presented. The system is based on continuous tunable optical TTD technique. Arbitrary multiple true-time delays to generate multiple broadband nulls can simultaneously be synthesised for each antenna element. The proposed structured are characterised both theoretically and experimentally. Experimental results demonstrating the principle of the true-time delay for null generations are presented. The maximum time delay measured for a wavelength tuning from 1530 to 1560 nm is 9.5 ns.     

Opto-VLSI-based tunable photonic RF filter

In this paper, an Opto-Very-Large-Scale-Integrated (Opto-VLSI) based tunable photonic radio frequency (RF) filter structure is proposed and numerically simulated. The structure comprises a reconfigurable Opto-VLSI processor capable of arbitrarily steering optical beams of different wavelengths, a diffraction grating for wavelength division demultiplexing, and high-dispersion fibres for true-time delaying RF-modulated wavebands. The proposed structure has the ability to generate arbitrary wavebands and weights for realizing any RF filter responses. The proof-of-concept of the tunable photonic RF signal processor is also experimentally demonstrated by tuning its free-spectral range and altering its shape factor through optical beam steering.     

Site-directed mutagenesis study on the thermal stability of a chemiric PQQ glucose dehydrogenase and its structural interpretation

We have previously reported that a chimeric pyrroloquinoline quinone (PQQ) glucose dehydrogenase (GDH), E97A3, which was made up of 97% of Escherichia coli PQQGDH sequence and 3% of Acinetobacter calcoaceticus PQQGDH, showed increased thermal stability compared with both parental enzymes. Site-directed mutagenesis studies were carried out in order to investigate the role of amino-acid substitution at the C-terminal region, Ser 771, of a chimeric PQQGDHs on their thermal stability. A series of Ser 771 substitutions of a chimeric PQQGDH, E99A1, confirmed that hydrophobic interaction governs the thermal stability of the chimeric enzymes. Comparison of the thermal denaturation of E. coli PQQGDH and E97A3 followed by far-ultraviolet (UV) circular dichroism (CD) spectroscopy revealed that E97 A3 acquired stability at the first step of denaturation, which is reversible, and where no significant secondary structure change was observed. These results suggested that the interaction between C-terminal and N-terminal regions may play a crucial role in maintaining the overall structure of β-propeller proteins.     

Film analysis employing subtarget effect using 355 nm Nd-YAG laser-induced plasma at low pressure

The applicability of spectrochemical analysis for liquid and powder samples of minute amount in the form of thin film was investigated using ultraviolet Nd-YAG laser (355 nm) and low-pressure ambient air. A variety of organic samples such as commercial black ink usually used for stamp pad, ginseng extract, human blood, liquid milk and ginseng powder was prepared as film deposited on the surface of an appropriate hard substrate such as copper plate or glass slide. It was demonstrated that in all cases studied, good quality spectra were obtained with very low background and free from undesirable contamination by the substrate elements, featuring ppm or even sub-ppm sensitivity and worthy of application for quantitative analysis of organic samples. The proper preparation of the films was found to be crucial in achieving the high quality spectra. It was further shown that much inferior results were obtained when the atmospheric-pressure (101 kPa) operating condition of laser-induced breakdown spectroscopy or the fundamental wavelength of the Nd-YAG laser was employed due to the excessive or improper laser ablation process.